Low-Resistance Electrode Design

ABSTRACT

A solution for designing a semiconductor device, in which two or more attributes of a pair of electrodes are determined to, for example, minimize resistance between the electrodes, is provided. Each electrode can include a current feeding contact from which multiple fingers extend, which are interdigitated with the fingers of the other electrode in an alternating pattern. The attributes can include a target depth of each finger, a target effective width of each pair of adjacent fingers, and/or one or more target attributes of the current feeding contacts. Subsequently, the device and/or a circuit including the device can be fabricated.

REFERENCE TO PRIOR APPLICATIONS

The current application is a continuation-in-part of co-pending U.S.patent application Ser. No. 12/791,259, titled “Low-Resistance ElectrodeDesign,” which was filed on 1 Jun. 2010, and which claims the benefit ofU.S. Provisional Application No. 61/217,532, titled “Low-resistancesemiconductor device,” which was filed on 1 Jun. 2009, both of which arehereby incorporated by reference.

TECHNICAL FIELD

The disclosure relates generally to semiconductor devices, and moreparticularly, to an improved electrode design for semiconductor devices.

BACKGROUND ART

On state resistance is an important characteristic of a semiconductordevice, such as a semiconductor device used in any of various switchingapplications. A low on state resistance in a planar device, such as afield effect transistor (FET) or a diode, is generally achieved by theuse of multi-finger structures for pairs of electrodes. The multi-fingerstructures increase the total periphery of each electrode.

The development and implementation of devices with a semiconductorstructure with extremely low sheet resistance, e.g., 200-300Ohms/square, presents new considerations in the design of devices withlow on state resistance. For example, when a low on state resistancedevice is manufactured using semiconductor layer(s) with very low sheetresistance, the resistance of the semiconductor layer becomes comparableto that of the metal electrodes supplying the current to the device. Inthis case, the current density along the device finger becomesnon-uniform. As a result, the device resistance does not decreaseinversely proportionally to the finger width (e.g., the size of thedimension of the finger that is perpendicular to the direction of thecurrent flow between the electrodes). Instead, as the finger width isincreased, the device resistance per unit finger width first decreases,flattens over a range of widths, and then increases as the width isfurther increased.

SUMMARY OF THE INVENTION

Aspects of the invention provide a solution for designing asemiconductor device, in which two or more attributes of a pair ofelectrodes are determined to, for example, minimize resistance betweenthe electrodes. Each electrode can include a current feeding contactfrom which multiple fingers extend, the fingers are interdigitated withthe fingers of the other electrode in an alternating pattern. Theattributes can include a target depth of each finger, a target effectivewidth of each pair of adjacent fingers, and/or one or more targetattributes of the current feeding contacts. Subsequently, the deviceand/or a circuit including the device can be fabricated. In this manner,a low total device impedance can be achieved.

A first aspect of the invention provides a method of designing asemiconductor device, the method comprising: configuring a set ofattributes of an interface between a first electrode to a semiconductorstructure of the semiconductor device and a second electrode to thesemiconductor structure, wherein each electrode includes a currentfeeding contact and a plurality of fingers extending therefrom, andwherein the plurality of fingers of the first and second electrodes areadjacent to each other in an alternating pattern, the configuringincluding determining at least one target attribute of the currentfeeding contact of each of the first and second electrodes based on atleast one of: a target depth, d_(FING), for each of the plurality offingers, a target effective width, W, of each pair of adjacent fingersof the first electrode and the second electrode, an impedance of thecurrent feeding contact per unit width, Z_(CMB), and an impedance of apair of adjacent fingers with the semiconductor structure there betweenper unit width, Z_(FINGSC).

A second aspect of the invention provides a method of fabricating asemiconductor device, the method comprising: designing the semiconductordevice, wherein the designing includes configuring a set of attributesof an interface between a first electrode to a semiconductor structureof the semiconductor device and a second electrode to the semiconductorstructure, wherein each electrode includes a current feeding contact anda plurality of fingers extending therefrom, and wherein the plurality offingers of the first and second electrodes are adjacent to each other inan alternating pattern, the configuring including determining at leastone target attribute of the current feeding contact of each of the firstand second electrodes based on at least one of: a target depth,d_(FING), for each of the plurality of fingers, a target effectivewidth, W, of each pair of adjacent fingers of the first electrode andthe second electrode, an impedance of the current feeding contact perunit width, Z_(CMB), and an impedance of a pair of adjacent fingers withthe semiconductor structure there between per unit width, Z_(FINGSC),and forming each of the first and second electrodes on the semiconductorstructure according to the design.

A third aspect of the invention provides a method comprising: designinga semiconductor device, wherein the designing includes configuring a setof attributes of an interface between a first electrode to asemiconductor structure of the semiconductor device and a secondelectrode to the semiconductor structure, wherein each electrodeincludes a current feeding contact and a plurality of fingers extendingtherefrom, and wherein the plurality of fingers of the first and secondelectrodes are adjacent to each other in an alternating pattern, theconfiguring including: determining a first target value for an attributein the set of attributes based on a set of operating frequencies for thedevice, wherein the target value is calculated to optimize the attributefor performance of the device at a set of target operating frequencies;determining a second target value for another attribute in the set ofattributes based on the first target value; and determining at least onetarget attribute of the current feeding contact of each of the first andsecond electrodes based on at least one of: a target depth, d_(FING,)for each of the plurality of fingers, a target effective width, W, ofeach pair of adjacent fingers of the first electrode and the secondelectrode, an impedance of the current feeding contact per unit width,Z_(CMB), and an impedance of a pair of adjacent fingers with thesemiconductor structure there between per unit width, Z_(FINGSC).

Other aspects of the invention provide methods, systems, programproducts, and methods of using and generating each, which include and/orimplement some or all of the actions described herein. The illustrativeaspects of the invention are designed to solve one or more of theproblems herein described and/or one or more other problems notdiscussed.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the disclosure will be more readilyunderstood from the following detailed description of the variousaspects of the invention taken in conjunction with the accompanyingdrawings that depict various aspects of the invention.

FIGS. 1A and 1B show top and side views, respectively, of anillustrative device according to an embodiment.

FIG. 1C shows a top view of an illustrative pair of adjacent fingersaccording to an embodiment.

FIG. 2 shows an illustrative diagram of the dependence of the impedanceof a device on the width of the electrodes according to an embodiment.

FIGS. 3A and 3B show illustrative circular electrode configurationsaccording to embodiments.

FIG. 4 shows a portion of another illustrative electrode configurationfor a device according to an embodiment.

FIG. 5 shows an illustrative flow diagram for fabricating a circuitaccording to an embodiment.

It is noted that the drawings may not be to scale. The drawings areintended to depict only typical aspects of the invention, and thereforeshould not be considered as limiting the scope of the invention. In thedrawings, like numbering represents like elements between the drawings.

DETAILED DESCRIPTION OF THE INVENTION

As indicated above, aspects of the invention provide a solution fordesigning a semiconductor device, in which two or more attributes of apair of electrodes are determined to, for example, minimize resistancebetween the electrodes. Each electrode can include a current feedingcontact from which multiple fingers extend, the fingers areinterdigitated with the fingers of the other electrode in an alternatingpattern. The attributes can include a target depth of each finger, atarget effective width of each pair of adjacent fingers, and/or one ormore target attributes of the current feeding contacts. Subsequently,the device and/or a circuit including the device can be fabricated. Inthis manner, a low total device impedance can be achieved. As usedherein, unless otherwise noted, the term “set” means one or more (i.e.,at least one) and the phrase “any solution” means any now known or laterdeveloped solution.

Turning to the drawings, FIGS. 1A and 1B show top and side views,respectively, of an illustrative device 10 according to an embodiment.In general, device 10 comprises a planar semiconductor device with alateral layout. To this extent, device 10 can comprise a highlyresistive substrate 12 with a semiconductor structure 14 comprising oneor more semiconducting layers formed thereon. Substrate 12 can compriseany type of substrate, such as sapphire, silicon, silicon carbide, orany other semiconductor or dielectric materials. Semiconductor structure14 can comprise, for example: a group-III nitride heterostructure, whichincludes two or more layers of materials selected from the group-IIInitride material system (e.g., Al_(X)In_(Y)Ga_(1-X-Y)N, where 0≦X, Y≦1,and X+Y≦1 and/or alloys thereof); a group-III arsenide heterostructure,which includes two or more layers of materials selected from thegroup-III arsenide material system (e.g., Al_(X)Ga_(1-X)As, where 0≦X≦1and/or alloys thereof); and/or the like.

Device 10 is shown including a pair of electrodes 20, 22. In order todesign the semiconductor device 10, a type of contact to thesemiconductor structure 14 can be selected for each electrode 20, 22using any solution. Each electrode 20, 22 can comprise, for example, ametal, and form any type of contact to the semiconductor structure 14.For example, each electrode 20, 22 can form an ohmic contact, acapacitively-coupled contact, a composite conducting capacitive coupledcontact, and/or the like to the semiconductor structure 14. Electrodes20, 22 can form the same type of contact or different types of contactsto the semiconductor structure 14 for a particular device 10, dependingon the desired application and/or operating characteristics for thedevice 10.

Also as part of designing the semiconductor device 10, a shapeconfiguration of the electrodes 20, 22 and the corresponding locationsof the electrodes 20, 22 can be designed. The shape configuration can beselected/designed to provide one or more benefits to the operation ofthe semiconductor device 10 using any solution. For example, asillustrated, each electrode 20, 22 can comprise a multi-finger electrodehaving a comb configuration, which includes multiple fingers, such asfingers 20A-20C, 22A-22C, respectively, electrically connected inparallel by a current feeding contact 24A, 24B from which each finger20A-20C, 22A-22C, respectively extends. The respective fingers 20A-20C,22A-22C of each electrode 20, 22 can be physically arranged in analternating manner (e.g., interdigitated). In operation, current canflow from one electrode 20, 22 to the other electrode 20, 22. Forexample, electrode 20 can comprise a source contact, while electrode 22comprises a drain contact for the device 10. In this case, under forwardbias operating conditions of device 10, current can flow from thefingers 20A-20C of electrode 20 to the fingers 22A-22C of electrode 22via the semiconductor structure 14. To this extent, the current canenter fingers 20A-20C via current feeding contact 24A and leave fingers22A-22C via current feeding contact 24B.

FIG. 1C shows a top view of an illustrative pair of adjacent fingers20A, 22A according to an embodiment. As illustrated, each finger 20A,22A comprises a corresponding depth, d_(FING), and each pair of fingers20A, 22A on electrodes 20, 22 comprises a corresponding effective width,W. The effective width W of each pair of fingers 20A, 22A is a size ofthe dimension of the pair of fingers 20A, 22A that is perpendicular tothe current flow direction between the electrodes 20, 22. Since thecurrent flows between adjacent fingers 20A, 22A primarily in ahorizontal direction in FIGS. 1A-1C, the effective width W cancorrespond to the portions of the vertical lengths of the fingers 20A,22A that are horizontally adjacent to one another. Moreover, thesemiconductor structure 14 (FIG. 1A) separating each pair of fingers20A, 22A has a corresponding length, L_(SC), over which the currenttravels. Additional measurements of electrodes 20, 22 include a depth ofthe current feeding contact 24A, 24B, d_(CMB), of each electrode and atotal length of the comb interface between the two electrodes 20, 22,L_(CMB), as shown in FIG. 1A.

An embodiment of the invention provides a solution for designing and/orfabricating electrodes 20, 22 of a semiconductor device 10 to achieve alower total resistance for device 10, which includes determining one ormore target attributes of the electrodes 20, 22. For example, a targeteffective width W of the respective electrodes 20, 22 can be determinedaccording to an embodiment. Subsequently, the design of thesemiconductor device 10 can include configuring the electrodes 20, 22according to the target effective width W. For example, one or moreattributes of the electrodes 20, 22 can be selected according to thetarget effective width W.

When the electrodes 20, 22 comprise multi-finger electrodes as shown inFIGS. 1A, 1B, the effective width W of each electrode 20, 22 correspondsto the effective width W of the respective pairs of fingers 20A, 22A and20B, 22B. The target effective width W can be selected to reduce theimpedance of the device 10, e.g., by reducing non-uniformity of thecurrent along the electrodes 20, 22 in a direction that is perpendicularto the current flow between the electrodes 20, 22. Such non-uniformitycan occur due to a finite resistance of the electrodes 20, 22 depositedover a highly-conducting semiconductor structure 14. In an illustrativeembodiment, the target effective width W of electrodes 20, 22corresponds to the effective width at which the impedance of the device10 is close to the impedance obtained with ideally conducting metalelectrodes 20, 22.

FIG. 2 shows an illustrative diagram of the dependence of the impedanceof a device, such as device 10 (FIG. 1), on the effective width W of theelectrodes 20A, 22A according to an embodiment. As illustrated in theinset of the diagram, the input current can enter the top electrode 20Afrom the left and leave the bottom electrode 22A from the right. If aresistance of the metal of each electrode 20A, 22A is zero, the topelectrode 20A and bottom electrode 22A would be equipotential, and thecurrent density through the semiconductor structure 14 (FIG. 1) betweenthe electrodes 20A, 22A would be uniform from left to right in theinset. However, due to a finite resistance of the metal of theelectrodes 20A, 22A, the current creates a voltage drop along theelectrodes 20A, 22A causing a current density to decrease in the centralpart of the electrodes 20A, 22A.

The non-uniformity of the current along the effective width W of theelectrodes 20A, 22A can be derived from the signal propagation along adistributed line formed by a series impedance of the electrodes 20A, 22Aand a shunting admittance of the semiconductor structure 14 connectedbetween the electrodes 20A, 22A. From the general transmission linetheory, the propagation constant in such a Z-Y line is γ_(FING)=√{squareroot over (Z₁Y₁)}, where Z₁ and Y₁ are the line series impedance andshunting admittance per unit length, respectively. For the transmissionline described herein, Z₁=2×Z_(FING) and Y₁=Y_(SC)=1/Z_(SC), whereZ_(FING) is an impedance of a metal electrode 20A, 22A per unit widthand Z_(SC) is an impedance of the semiconducting structure 14 betweenthe electrodes 20A, 22A per unit width. Z_(FING) can be calculated, forexample, using the formula Z_(FING)=R_(SHFING)/d_(FING), whereR_(SHFING) is the sheet resistance of a finger and d_(FING) is the depthof the finger. A factor of two can be used in calculating Z₁ to accountfor the resistances of the two electrodes 20A, 22A connected in seriesin each unit cell of the Z-Y transmission line. Similarly, theresistances of the two electrodes 20A, 22A can be summed whencalculating Z₁.

From these equations, the propagation constant for the distributedtransmission line along the fingers can be calculated by the equation,γ_(FING) =√{square root over (2Z_(FING)/Z_(SC))}. As the effective widthW of the pair of electrodes 20A, 22A increases, a contribution of themetal electrodes 20A, 22A to the total device impedance increases aswell. As a result, the device impedance, Z ₀, decreases slower with theeffective width W as compared to a structure with zero-resistivityelectrodes 20A, 22A. When the product, γ_(FING)*W, exceeds unity, thedevice impedance Z₀ can increase with the effective width W.

An embodiment determines a target effective width W of electrodes 20A,22A as an effective width where γ_(FING)*W≦2. In this case, the totalimpedance per pair of electrodes 20A, 22A is close to the impedance of astructure with ideally conducting electrodes 20A, 22A (e.g., zero metalresistance). Similarly, an embodiment provides fabrication ofmulti-finger electrodes 20, 22 (FIG. 1) in which a target effectivewidth W of each finger pair, such as a pair of fingers 20A, 22A and apair of fingers 20B, 22B, is determined such that γ_(FING)*W≦2 toachieve a low total impedance Z₀ of the corresponding device 10.

Returning to FIGS. 1A-1C, one or more other attributes of the electrodes20, 22 can be determined based on a total device resistance. Forexample, an embodiment provides a solution for designing and/orfabricating electrodes 20, 22 that includes determining one or more of:a total number of fingers 20A-20B, 22A-22B for each electrode 20, 22comprising a comb configuration; a target depth, d_(FING), of eachfinger 20A-20B, 22A-22B; a target length of each finger 20A-20B,22A-22B; a target depth, d_(CMB), of the current feeding contact 24A,24B of each electrode 20, 22, respectively; a total length, L_(CMB), ofthe interdigitated comb configuration of the two electrodes 20, 22;and/or the like.

For example, a target depth, d_(FING), of each finger 20A-20B, 22A-22Bcan be determined based on a characteristic contact transfer length,L_(TR), of a junction between electrodes 20, 22 and semiconductorstructure 14. The characteristic contact transfer length L_(TR) can bedetermined, for example, using the transmission line measurement (TLM)technique. The target depths of the fingers can be selected to provide aminimal resistance to the current flow through the fingers. In anembodiment, a target depth d_(FING) for the first finger 20C and lastfinger 22C of the interface of electrodes 20, 22 can comprise a depthd_(FING)≧3*L_(TR) (e.g., since each includes only a single adjacentfinger in the structure), while the remaining fingers of each electrode20, 22 can comprise a depth d_(FING)≧6*L_(TR) (e.g., since each includestwo adjacent fingers in the structure). Additionally, the design caninclude determining a target effective width W of each pair of fingers.For example, when the target depths d_(FING) of the fingers are asdescribed above, the target effective width W of each pair of fingerscan be selected such that γ_(FING)*W≦2. As illustrated in FIG. 2, suchan effective width will provide a minimal impedance for the device. Atotal width of each finger can comprise the effective width W plusapproximately the length of the semiconductor between adjacent fingers,L_(SC). Similarly, a total width between the current feeding contacts24A, 24B can comprise the effective width W plus approximately 2*L_(SC).

An embodiment of the design further includes determining a target totallength L_(CMB) of the interdigitated comb configuration of the twoelectrodes 20, 22. To this extent, the design can include determining animpedance of the current feeding contacts 24A, 24B, Z_(CMB), todetermine the target total length L_(CMB). Z_(CMB) can be calculated,for example, using the formula Z_(CMB)=R_(SHCMB)/d_(CMB), whereR_(SHCMB) is the sheet resistance of the current feeding contact andd_(CMB) is the depth of the current feeding contact. Z_(CMB) can be usedto determine a propagation constant of the distributed transmission linealong the current feeding contacts 24A, 24B, γ_(CMB). For example,γ_(CMB) can be calculated by the equation, γ_(CMB)=√{square root over(2Z_(CMB)/Z_(FINGSC))}, where Z_(FINGSC) is the unit-length resistanceof the pair of fingers with the semiconductor material in between.Z_(FINGSC) can be calculated, for example, using the formulaZ_(FINGSC)=R_(SHSC)×L_(SC)/W*(2d_(FING)+L_(SC)), where R_(SHSC) is thesheet resistance of the semiconductor structure 14. Subsequently,L_(CMB) can be selected to provide a minimal resistance to the currentflow. For example, similar to the effective width W as illustrated inFIG. 2, L_(CMB) can be selected such that L_(CMB)*γ_(CMB)≦2. Inparticular, a similar relationship between the total length of the combconfiguration can apply as described above with respect to therelationship of the effective width W of each finger pair. Since γ_(CMB)depends on d_(CMB), an embodiment of the design can determine a targetdepth d_(CMB) of the current feeding contact 24A, 24B of each electrode20, 22 that satisfies L_(CMB)*γ_(CMB)≦2. For example, when a targettotal device impedance Z₀ is given, the design can derive a requirednumber of finger pairs and L_(CMB) from the total impedance. In anyevent, from L_(CMB), a total length of the current feeding contact ofeach electrode 20, 22 can be derived, e.g., by subtracting a depth of anend finger 20C, 22C and the length of the semiconductor between adjacentfingers, L_(SC).

It is understood that the various target attributes can be determinedfor alternative electrode configurations. For example, FIGS. 3A and 3Bshow illustrative circular electrode configurations according toembodiments. As illustrated in FIG. 3A, the electrode configurationincludes a pair of electrodes 30, 32, each of which comprises a currentfeeding contact 34A, 34B, respectively, and a plurality of electrodefingers 30A-30B, 32A-32B, respectively. Each electrode finger 30A-30B,32A-32B comprises a partial elliptical (e.g., circular) shape. In thiscase, a solution for designing and/or fabricating electrodes 30, 32 caninclude determining one or more of: a total number of fingers 30A-30B,32A-32B for each electrode 30, 32; a target depth of each finger30A-30B, 32A-32B; a target length of each finger 30A-30B, 32A-32B; atarget depth of the current feeding contact 34A, 34B of each electrode30, 32, respectively; a total length of the interdigitated combconfiguration of the two electrodes 30, 32; and/or the like. Electrodes30, 32 can be configured to include any number of pairs of fingers30A-30B, 32A-32B.

Additionally, as illustrated in FIG. 3B, each finger 30A-30B, 32A-32Bcan comprise a plurality of extensions, such as extensions 36A, 36B, oneor more target attributes of which also can be determined as describedherein. The target attributes of the extensions can be determinedsimilar to the target attributes of the fingers shown in FIG. 1C anddescribed herein, where each extension corresponds to a finger, and eachfinger corresponds to a current feeding contact. For example, a targetdepth of each extension, d_(EXT), can be determined similar to thetarget depth of each finger d_(FING) described herein, and a targeteffective width of a pair of adjacent extensions, W_(EXT), can bedetermined similar to the target effective width of a pair of adjacentfingers W described herein. To this extent, the target depth of eachextension d_(EXT) can be selected to such that d_(EXT)≧3*L_(TR) (for theend extensions) or d_(EXT)≧6*L_(TR) (for all interior extensions).Similarly, the target effective width of each pair of adjacentextensions W_(EXT) can be selected such that γ_(EXT)*W_(EXT)≦2, whereγ_(EXT)=√{square root over (2Z_(EXT)/Z_(SC))}. While extensions 36A, 36Bare only shown and described with reference to the partially ellipticalfingers, it is understood that the fingers of FIG. 1A could be similarlyconfigured with extensions between the pairs of fingers.

To this extent, target value(s) for one or more of the variousattributes can be determined using similar formulas as described herein.However, one or more of the formulas can be modified to account for thecircular configuration of electrodes 30, 32. For example, the targeteffective width W for a pair of fingers, such as fingers 30B, 32B, canbe approximately correspond to an inner circumference of the largerfinger (e.g., finger 32B). To this extent, a diameter, d, of the largerfinger can be selected such that πdγ≦2, where γ is calculated based onthe impedance of the electrodes 30, 32 and a corresponding semiconductorstructure using the same formula described above in calculatingγ_(FING).

A target value for one or more attributes, such as the characteristiccontact transfer length, L_(TR), the propagation constant, γ, and/or thelike, can vary for an operating frequency of the device 10. To thisextent, the target value(s) for one or more of the various attributesalso can be determined based on a set of operating frequencies. Forexample, a plurality of optimal values for an attribute can bedetermined for direct current (DC) operation (corresponding to anoperating frequency of zero) and one or more target operatingfrequencies for the device 10. Each optimal value can correspond to anoptimum value for the corresponding attribute when the device isoperated at the corresponding operating frequency.

The frequency dependence of the attribute can be accounted for whencalculating the optimal value using any solution. Illustrative solutionsinclude, but are not limited to, representing current carryingelement(s) by distributed equivalent circuits representing specificresistive, inductive, and capacitive components, solving differentialequations for the current distribution accounting for such components,solving Maxwell equations accounting or not accounting for radiationresistance, by measuring the frequency dependent parameter (e.g.,S-parameters, and/or the like), and/or the like. Subsequently, theplurality of optimal values can be used to determine a target value forthe attribute, which can allow for a trade-off of the optimal values tooptimize the overall performance of the device 10 using any solution.For example, the plurality of optimal values can be used to optimize aset of parameters for each operating frequency, create an objectivefunction using the optimized sets of parameters, and select a set oftarget values for one or more attributes of the device 10 at a desiredlocation on the objective function. The target value for an attributealso can be used in calculating the target values for one or more of theother various attributes, e.g., using one or more of the calculationsdescribed herein.

Aspects of the invention described herein can be applied to the designand fabrication of various types of devices for which operation of thedevice is improved when resistance between electrodes 20, 22 is reduced.For example, device 10 or a device with the electrode configuration ofFIG. 3 can comprise a diode, such as a large periphery diode, a highcurrent Schottky diode, a p-n junction diode, and/or the like. To thisextent, one or more electrodes 20, 22 or 30, 32 can form a non-linearcontact with the semiconductor structure 14. For example, electrodes 20,22 can comprise different diode contacts, e.g., ohmic and Schottky orcontacts to p- and n-regions of the semiconductor structure 14, and/orthe like.

FIG. 4 shows a portion of another illustrative electrode configurationfor a device 40 according to an embodiment. Device 40 can includemulti-finger electrodes 20, 22 formed on a semiconductor structure 14.The fingers of electrodes 20, 22 can be designed to have the targeteffective width W as described herein. Additionally, device 40 includesa series of gate electrodes 42A-42D formed between the fingers of theelectrodes 20, 22. Gate electrodes 42A-42D can be operated toselectively allow the flow of current between the fingers of electrodes20, 22 using any solution.

In any event, after the electrodes have been configured, a device, suchas device 10 (FIG. 1) or device 40, can be fabricated using anysolution. To this extent, the fabrication of the device 10, 40 caninclude forming each of the corresponding electrodes of approximatelythe target effective width W as determined herein. Devices 10, 40 caneach be implemented as a component in any of various types of circuits.For example, device 40 can be configured to operate as a field effecttransistor (FET) within a circuit. To this extent, device 40 cancomprise a FET that is used as a solid-state switch, an amplifier in aswitching mode (e.g., class E, F), and/or the like.

While shown and described herein as a method of designing and/orfabricating a semiconductor device, it is understood that aspects of theinvention further provide various alternative embodiments. For example,in one embodiment, the invention provides a method of designing and/orfabricating a circuit that includes one or more of the semiconductordevices designed and fabricated as described herein.

To this extent, FIG. 5 shows an illustrative flow diagram forfabricating a circuit 126 according to an embodiment. Initially, a usercan utilize a device design system 110 to generate a device design 112using a method described herein. The device design 112 can be used by adevice fabrication system 114 to generate a set of physical devices 116according to the features defined by the device design 112. Similarly,the device design 112 can be provided to a circuit design system 120(e.g., as an available component for use in circuits), which a user canutilize to generate a circuit design 122. The circuit design 122 caninclude a device designed using a method described herein. In any event,the circuit design 122 and/or one or more physical devices 116 can beprovided to a circuit fabrication system 124, which can generate aphysical circuit 126 according to the circuit design 122. The physicalcircuit 126 can include one or more devices 116 designed using a methoddescribed herein.

In another embodiment, the invention provides a device design system 110for designing and/or a device fabrication system 114 for fabricating asemiconductor device 116 by applying the method described herein. Inthis case, the system 110, 114 can comprise a general purpose computingdevice, which is programmed to implement a method of designing and/orfabricating the semiconductor device 116 as described herein. Similarly,an embodiment of the invention provides a circuit design system 120 fordesigning and/or a circuit fabrication system 124 for fabricating acircuit 126 that includes at least one device 116 designed and/orfabricated using a method described herein. In this case, the system120, 124 can comprise a general purpose computing device, which isprogrammed to implement a method of designing and/or fabricating thecircuit 126 including at least one semiconductor device 116 as describedherein.

In still another embodiment, the invention provides a computer programfixed in at least one computer-readable medium, which when executed,enables a computer system to implement a method of designing and/orfabricating a semiconductor device as described herein. For example, thecomputer program can enable the device design system 110 to generate thedevice design 112 as described herein. To this extent, thecomputer-readable medium includes program code, which implements some orall of a process described herein when executed by the computer system.It is understood that the term “computer-readable medium” comprises oneor more of any type of tangible medium of expression, now known or laterdeveloped, from which a copy of the program code can be perceived,reproduced, or otherwise communicated by a computing device. Forexample, the computer-readable medium can comprise: one or more portablestorage articles of manufacture; one or more memory/storage componentsof a computing device; paper; and/or the like.

In another embodiment, the invention provides a method of providing acopy of program code, which implements some or all of a processdescribed herein when executed by a computer system. In this case, acomputer system can process a copy of the program code to generate andtransmit, for reception at a second, distinct location, a set of datasignals that has one or more of its characteristics set and/or changedin such a manner as to encode a copy of the program code in the set ofdata signals. Similarly, an embodiment of the invention provides amethod of acquiring a copy of program code that implements some or allof a process described herein, which includes a computer systemreceiving the set of data signals described herein, and translating theset of data signals into a copy of the computer program fixed in atleast one computer-readable medium. In either case, the set of datasignals can be transmitted/received using any type of communicationslink.

In still another embodiment, the invention provides a method ofgenerating a device design system 110 for designing and/or a devicefabrication system 114 for fabricating a semiconductor device asdescribed herein. In this case, a computer system can be obtained (e.g.,created, maintained, made available, etc.) and one or more componentsfor performing a process described herein can be obtained (e.g.,created, purchased, used, modified, etc.) and deployed to the computersystem. To this extent, the deployment can comprise one or more of: (1)installing program code on a computing device; (2) adding one or morecomputing and/or I/O devices to the computer system; (3) incorporatingand/or modifying the computer system to enable it to perform a processdescribed herein; and/or the like.

The foregoing description of various aspects of the invention has beenpresented for purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the precise formdisclosed, and obviously, many modifications and variations arepossible. Such modifications and variations that may be apparent to anindividual in the art are included within the scope of the invention asdefined by the accompanying claims.

1. A method of designing a semiconductor device, the method comprising:configuring a set of attributes of an interface between a firstelectrode to a semiconductor structure of the semiconductor device and asecond electrode to the semiconductor structure, wherein each electrodeincludes a current feeding contact and a plurality of fingers extendingtherefrom, and wherein the plurality of fingers of the first and secondelectrodes are adjacent to each other in an alternating pattern, theconfiguring including determining at least one target attribute of thecurrent feeding contact of each of the first and second electrodes basedon at least one of: a target depth, d_(FING), for each of the pluralityof fingers, a target effective width, W, of each pair of adjacentfingers of the first electrode and the second electrode, an impedance ofthe current feeding contact per unit width, Z_(CMB), and an impedance ofa pair of adjacent fingers with the semiconductor structure therebetween per unit width, Z_(FINGSC).
 2. The method of claim 1, whereinthe at least one target attribute of the current feeding contactcomprises a depth of the current feeding contact.
 3. The method of claim1, wherein the determining the at least one target attribute comprisesdetermining a total length of the current feeding contact.
 4. The methodof claim 1, wherein the configuring further includes determining thetarget depth, d_(FING), for each of the plurality of fingers based on acharacteristic contact transfer length for a junction between thefingers and the semiconductor device, L_(TR).
 5. The method of claim 4,wherein the determining the target depth includes selecting the targetdepth for each end finger such that d_(FING)≧3*L_(TR), and selecting thetarget depth for every other finger such that d_(FING)≧6*L_(TR).
 6. Themethod of claim 4, further comprising determining a target value for thecharacteristic contact transfer length based on a set of operatingfrequencies for the device, wherein the target value is calculated tooptimize the characteristic contact transfer length for performance ofthe device at a set of target operating frequencies for the device. 7.The method of claim 1, wherein the configuring further includesdetermining the target effective width, W, of each pair of adjacentfingers of the first electrode and the second electrode based on thetarget depth, an impedance of at least one finger per unit width,Z_(FING), and an impedance of a portion of the semiconductor structurebetween the pair of adjacent fingers per unit width, Z_(SC).
 8. Themethod of claim 7, wherein the determining the target effective widthincludes selecting the target effective width such that γ_(FING)*W≦2,where γ_(FING)=√{square root over (2Z_(FING)/Z_(SC))}.
 9. The method ofclaim 1, wherein the determining the at least one target attributeincludes selecting the at least one target attribute such that a totallength of the interface between the first and second electrodes,L_(CMB)*γ_(CMB)≦2, where γ_(CMB)=√{square root over(2Z_(CMB)/Z_(FINGSC))}.
 10. The method of claim 1, further comprisingdetermining a target value for a propagation constant of a distributedtransmission line along at least one of: two adjacent fingers or thecurrent feeding contacts based on a set of operating frequencies for thedevice, wherein the target value is calculated to optimize thepropagation constant for performance of the device at a set of targetoperating frequencies for the device.
 11. The method of claim 1, whereineach pair of adjacent fingers further includes a plurality of extensionsextending there between, wherein the plurality of extensions for eachpair of adjacent fingers are adjacent to each other in an alternatingpattern, and wherein the configuring further includes determining atleast one of: a target depth for each of the plurality of extensions ora target effective width for each pair of adjacent extensions for eachpair of adjacent fingers.
 12. A method of fabricating a semiconductordevice, the method comprising: designing the semiconductor device,wherein the designing includes configuring a set of attributes of aninterface between a first electrode to a semiconductor structure of thesemiconductor device and a second electrode to the semiconductorstructure, wherein each electrode includes a current feeding contact anda plurality of fingers extending therefrom, and wherein the plurality offingers of the first and second electrodes are adjacent to each other inan alternating pattern, the configuring including determining at leastone target attribute of the current feeding contact of each of the firstand second electrodes based on at least one of: a target depth,d_(FING,) for each of the plurality of fingers, a target effectivewidth, W, of each pair of adjacent fingers of the first electrode andthe second electrode, an impedance of the current feeding contact perunit width, Z_(CMB), and an impedance of a pair of adjacent fingers withthe semiconductor structure there between per unit width, Z_(FINGSC);and forming each of the first and second electrodes on the semiconductorstructure according to the design.
 13. The method of claim 12, whereinthe at least one target attribute of the current feeding contactcomprises at least one of: a depth of the current feeding contact or atotal length of the current feeding contact.
 14. The method of claim 12,wherein the configuring further includes determining the target depth,d_(FING), for each of the plurality of fingers based on a characteristiccontact transfer length for a junction between the fingers and thesemiconductor device, L_(TR).
 15. The method of claim 14, wherein thedesigning further includes determining a target value for thecharacteristic contact transfer length based on a set of operatingfrequencies for the device, wherein the target value is calculated tooptimize the characteristic contact transfer length for performance ofthe device at a set of target operating frequencies for the device. 16.The method of claim 12, wherein the configuring further includesdetermining the target effective width, W, of each pair of adjacentfingers of the first electrode and the second electrode based on thetarget depth, an impedance of at least one finger per unit width,Z_(FING,) and an impedance of a portion of the semiconductor structurebetween the pair of adjacent fingers per unit width, Z_(SC).
 17. Themethod of claim 12, further comprising determining a target value for apropagation constant of a distributed transmission line along at leastone of: two adjacent fingers or the current feeding contacts based on aset of operating frequencies for the device, wherein the target value iscalculated to optimize the propagation constant for performance of thedevice at a set of target operating frequencies for the device.
 18. Asemiconductor device fabricated using the method of claim
 12. 19. Amethod comprising: designing a semiconductor device, wherein thedesigning includes configuring a set of attributes of an interfacebetween a first electrode to a semiconductor structure of thesemiconductor device and a second electrode to the semiconductorstructure, wherein each electrode includes a current feeding contact anda plurality of fingers extending therefrom, and wherein the plurality offingers of the first and second electrodes are adjacent to each other inan alternating pattern, the configuring including: determining a firsttarget value for an attribute in the set of attributes based on a set ofoperating frequencies for the device, wherein the target value iscalculated to optimize the attribute for performance of the device at aset of target operating frequencies; determining a second target valuefor another attribute in the set of attributes based on the first targetvalue; and determining at least one target attribute of the currentfeeding contact of each of the first and second electrodes based on atleast one of: a target depth, d_(FING), for each of the plurality offingers, a target effective width, W, of each pair of adjacent fingersof the first electrode and the second electrode, an impedance of thecurrent feeding contact per unit width, Z_(CMB), and an impedance of apair of adjacent fingers with the semiconductor structure there betweenper unit width, Z_(FINGSC).
 20. The method of claim 19, wherein theattribute is a characteristic contact transfer length for a junctionbetween the fingers and the semiconductor device, L_(TR).
 21. The methodof claim 19, wherein the attribute is a target value for a propagationconstant of a distributed transmission line along at least one of: twoadjacent fingers or the current feeding contacts.
 22. The method ofclaim 19, further comprising fabricating the semiconductor device,wherein the fabricating includes forming each of the first and secondelectrodes on the semiconductor structure according to the design.
 23. Asemiconductor device fabricated using the method of claim 22.